The SZ effect as a probe of violent cluster mergers Eiichiro - PowerPoint PPT Presentation

The SZ effect as a probe of violent cluster mergers Eiichiro Komatsu (Max-Planck-Institut für Astrophysik) Ringberg Workshop, November 22, 2012 1

Purpose of This Talk • Show (hopefully, give an observational proof) that high-spatial resolution (~10”) SZ mapping observations are a powerful probe of violent cluster mergers. 2

Collaborators (1998–2012) • Takuya Akahori (KASI) • Tai Oshima (Nobeyama) • Makoto Hattori (Tohoku Univ.) • Naomi Ota (Tokyo Univ. of Science) • Daisuke Iono (Nobeyama) • Shigehisa Takakuwa (ASIAA) • Ryohei Kawabe (NAOJ) • Motokazu Takizawa (Yamagata Univ.) • Tetsu Kitayama (Toho Univ.) • Takahiro Tsutsumi (NRAO) • Kotaro Kohno (Univ. of Tokyo) • Sabine Schindler (Univ. of Innsbruck) • Nario Kuno (Nobeyama) • Yasushi Suto (Univ. of Tokyo) • Hiroshi Matsuo (NAOJ) • Kenkichi Yamada (Toho Univ.) • Koichi Murase (Saitama Univ.) • Kohji Yoshikawa (Univ. of Tsukuba) 3

Papers • Komatsu et al., ApJL, 516, L1 (1999) [SCUBA@350GHz] • Komatsu et al., PASJ, 53, 57 (2001) [NOBA@150GHz] • Kitayama et al., PASJ, 56, 17 (2004) [Analysis w/ Chandra] • Ota et al., A&A, 491, 363 (2008) [Suzaku] • Yamada et al., PASJ, 64, 101 (2012) [ALMA Simulation] 4

Target: Bright, Massive, and Compact • RXJ1347–1145 • z =0.451 (10”=59 kpc) • L X,bol ~2x10 46 erg/s • M tot (<2Mpc)~1x10 15 M sun • Cluster Mean T X ~13keV • θ core ~8 arcsec (47 kpc) • y~8x10 -4 5

High Spatial Resolution SZ Mapping Observations • SCUBA /JCMT@350GHz BIMA Data • 15 arcsec FWHM Beam (Carlstrom et al.) of RXJ1347–1145 • Observed in 1998&1999 • rms=5.3 mJy/beam (8 hours) • NOBA /Nobeyama 45m@150GHz Our Beam • 13 arcsec FWHM Beam BIMA Beam • Observed in 1999&2000 • rms=1.6 mJy/beam (24 hours) 6

Nobeyama Bolometer Array • NOBA = 7-element bolometer array working at λ =2mm • Made by Nario Kuno (NRO) and Hiroshi Matsuo (NAOJ) in 30 1993 50 7

X-ray Observations • ROSAT , HRI (Schindler et al. 1997) • Sensitive up to ~ 2 keV • 35.6 ks (HRI) • Chandra , ACIS-S3 (Allen et al. 2002), ACIS-I (archived) • Sensitive up to ~7 keV • 18.9 ks (ACIS-S3), 56 ks (ACIS-I) • Suzaku , XIS and HXD (Ota et al. 2008) • Sensitive up to ~12 keV (XIS); ~60 keV (HXD/PIN) • 149 ks (XIS), 122 ks (HXD) 8

Komatsu et al. (2001) SZ “Hot Spot” • Significant offset between the SZ peak and the cluster 9 center.

Komatsu et al. (2001) SZ saw it, but ROSAT missed • ROSAT data indicated that this cluster was a relaxed, 10 regular cluster. The SZ data was not consistent with that.

Komatsu et al. (2001) 11

Allen et al. (2002) Confirmed by Chandra • Allen et al. (2002) estimated ~18 keV toward this direction from Chandra spectroscopy. • But, Chandra is sensitive only up to ~7(1+z)=10 keV... 12

X-ray + SZ Joint • The SZ effect is sensitive to arbitrarily high temperature. • X-ray spectroscopy is not. • Combine the X-ray brightness and the SZ brightness to derive the electron temperature: • I SZ is proportional to n e T e L, I X is proportional to n e2 Λ (T e )L -> Solve for T e (and L) • No X-ray spectroscopy is used 13

Kitayama et al. (2004) 14

Komatsu et al. (1999, 2001); Kitayama et al. (2004) Images of the SZ data • Spatially resolved SZ images in 350 GHz (increment) and 150 GHz (decrement) 15

Relativistic Correction • At such a high T e that we are going to deal with (~20 keV), the relativistic correction must be taken into SCUBA account. • The suppression of NOBA the signal due to the relativistic correction diminishes the SZ at 350GHz more than that at 150GHz. 16

“SE” (South-East) Quadrant • We exclude the central part that is contaminated by the ~4mJy point source, and treat the SE quadrant separately from the rest of the cluster (which we shall 17 call the “ambient component”).

Komatsu et al. (1999, 2001); Kitayama et al. (2004) SZ Radial Profiles • The excess SZ in the South-East quadrant is clearly seen. 18

X-ray Radial Profile SE Quadrant Others • The Chandra data also show the clear excess at ~20”. 19

Temperature Deprojection (Ambient Component) • SE quadrant is excluded. • Black : the temperature profile measured from the Chandra X-ray spectroscopy. • Red : the temperature profile measured from the spatially resolved SZ data + X-ray imaging, without spectroscopy. 20

What is this good for? • Spatially-resolved SZ + X-ray surface brightness observations give you the temperature profile, without spatially-resolved spectroscopic observations. • A powerful way of determining the temperature profiles from high-z clusters, where you may not get enough X-ray photons to do the spatially-resolved spectroscopy! • Why need temperature profiles? For determining accurate hydrostatic masses . 21

Excess Component: Derived Parameters • With the SZ data (150&350GHz) and the Chandra X-ray data • kT excess =28.5±7.3 keV • n excess =(1.49±0.59)x10 -2 cm -3 • L excess =240±183 kpc • y excess ~4x10 -4 • M gas ~2x10 12 M sun 22

Characterizing a merger in RXJ1347-1145 • A calculation of the shock (Rankine-Hugoniot condition) with: • pre-shock temp=kT 1 =12.7keV; post-shock=kT 2 =28.5keV • pre-shock density= ρ 1 =free; post-shock= ρ 2 =0.015 cm -3 • gamma=5/3 T 1 ρ 1 T 2 ρ 2 = • Solution: ρ 1 ~1/2.4 of the post-shock density 23

Characterizing a merger in RXJ1347-1145 • The Mach number of the pre-shock gas ~ 2, and the velocities of the pre-shock and post-shock gas are 3900 km/s & 1600 km/s. • Rather high velocity! • For more detailed modeling in the context of “gas sloshing,” see Johnson et al. (2012) 24

A Big Question • Do you believe these results? • This was the only dataset [before 2010] for which the spatially-resolved, high-resolution SZ data were available, and used to extract the cluster physics. • Can we get the same results using the X-ray data alone? • For Chandra, the answer is no: not enough sensitivity at >7(1+z)keV. • Suzaku can do this. 25

A Punch Line • With Suzaku’s improved sensitivity at ~10 keV, we could determine the temperature of the excess component using the X-ray data only . • And, the results are in an excellent agreement with the SZ+Chandra analysis. • Ota et al., A&A, 491, 363 (2008) 26

Suzaku Telescope • Japan-US X-ray satellite, formally known as ASTRO-E2 • X-ray Imaging Spectrometer (XIS) • X-ray CCD cameras; FOV=18’x18’; Beam=2’ • Three with 0.4– 12 keV; one with 0.2– 12 keV • Energy resolution~160eV at 6keV • Hard X-ray Detector (HXD) • One with 10–60 keV; another with 40–600keV • FOV=30’x30’ for 10–60keV, no imaging capability 27

XIS Image of RXJ1347–1145 “Cluster Region” • From one of the XIS 5’ cameras, in 0.5–10keV • FOV=18’x18’ Background Characterization 28

XIS Spectra H-like: rest frame 6.9 keV He-like: rest frame 6.7 keV (a) (b) 0.1 1 He � like Fe K � H � like Fe K � 0.1 counts/sec/keV counts/sec/keV 0.05 0.01 XIS0 XIS1 XIS0 XIS2 10 � 3 XIS3 0.02 � 4 � 2 0 2 4 � 4 � 2 0 2 4 � � 4 4.5 5 5.5 0.5 1 2 5 10 Energy [keV] Energy [keV] • Single-temperature fit yields kT e =12.86 +0.08-0.25 keV • But, it fails to fit the Fe line ratios - χ 2 =1320/1198 • The single-temperature model is rejected at 99.3% CL 29

Temperature From Line Ratio (b) 10 (He � like FeK � )/(H � like FeK � ) 1 0.1 5 10 15 20 kT [keV] • kT e =10.4 +1.0-1.3 keV - significantly cooler than the single- temperature fit, 12.86 +0.08-0.25 keV. 30

More Detailed Modeling • We tried the next-simplest model: two-temperature model, but it did not work very well either. • We know why: RXJ1347-1145 is more complicated than the two-component model. • The second component is localized, rather than distributed over the entire cluster. • A joint Chandra/Suzaku analysis allows us to take advantage of the Chandra’s spatial resolution and Suzaku’s spectroscopic sensitivity. 31

(a) “Subtract Chandra Projected Deprojected 20 from Suzaku” kT [keV] 10 5 • To make a long story short: 2 1 10 100 radius [arcsec] • We use the Chandra data outside of the excess region (SE region) to get the model for the ambient gas. • 6 components fit to 6 radial bins from 0” to 300”. • Then, subtract this ambient model from the Suzaku data. • Finally, fit the thermal plasma model to the residual. • And... 32

Results! (a) 1 10 � 7 10 � 6 10 � 5 10 � 4 10 � 3 0.01 0.1 HXD HXD data are counts/sec/keV consistent with the XIS thermal model; we did not find evidence for Excess Component non-thermal emission. � 4 � 2 0 2 4 � 1 10 • kT excess =25.3 +6.1-4.5 keV; n excess =(1.6±0.2)x10 -2 cm -3 Energy [keV] • Consistent with SZ+Chandra: • kT excess =28.5±7.3 keV, n excess =(1.49±0.59)x10 -2 cm -3 33

Proof of Principle • So, finally , we have a proof: • Yes, the high-spatial resolution SZ mapping combined with the X-ray surface brightness indeed gives the correct result . • And, we have found a candidate for the hottest gas clump known so far! 34